Cheap, yet beautiful alternatives include these LTM (M39 Leica Thread Mounts, which would work with your bessas with an LTM to M converter)
These are all Former Soviet Union LTM ~50mm
- Industar 61 L/D - VERY SHARP, lanthanum coated optics, very contrasty, nice bokeh ~USD$25
- Industar 61 - called the panda lens because of its silver and black rimming, i like these lens. I got mine with a FED-4 camera.
- Jupiter 8 - Zeiss Sonnar 50mm copy, pretty fast lens--f/2 ~USD$50
- Industar 50 - comes in the Elmar design or the rigid design. ~USD$45
- Industar 22 - Comes in elmar design, very nice. Coated, and has this lovely softness.
- Jupiter 3 - These are NICE lens.... very sharp, very fast lens, I think they were also modeled after Zeiss Sonnar's but they're nicer than the Jupiter 8's in some way. ~USD$100-120
Of course these lenses are unique, and sometimes the sellers on ebay don't do a good job at explaining their items that well, so I would recommend you buying from user Alex-photo on ebay. He is perhaps the best dealer to get lenses from. Very fair and cheap, shipping to the US isn't too bad either.
I would say Former Soviet Union lenses are nice backups, they're very replaceable, but you'll find yourself enjoying using them. I think that some of the older ones might be a bit frustrating to use in sunny weather because some of the former lenses do not have very sophisticated coating to prevent flares. A simple remedy would be a lenshood made from an Isopropanol rubbing alcohol bottle sprayed in matte black spray paint.
Ahh, and also, I reallly like the 50mm f/2 summicron's.... a gem of a lens.